Shared article

Skin Cancers

Introduction and Contents

 

In Caucasian populations, skin cancers, when grouped together, form the most commonly diagnosed human malignancy. Skin cancers are named after the type of cells that it is derived from. The three most common skin cancers are basal cell carcinomas, squamous cell carcinomas and melanomas in descending order of frequency. The first two comprise the majority of skin cancers and carry low morbidity and mortality, whilst melanomas are associated with a much higher degree of mortality due to its propensity to metastasize.

 

This revision article aims to give an overview of the different types of skin cancer, and will be covering the following areas:

  • Classification of skin types using the Fitzpatrick classification and its relationship to cancer.
  • The effects of UVA and UVB on the skin. 
  • The short and long term effects of sun exposure.
  • An overview of the different types of skin cancer. 
  • Pre-malignant conditions of the skin. 
  • Basal Cell Carcinomas. 
  • Squamous Cell Carcinomas. 
  • Melanomas. 

 

Types of UV light

 

UVB (B for Burn and Bad):

 - Very important in both sun burn + development of skin cancer.

 

UVA:

 - Increasing importance in development of skin cancer.

- Causes tanning but not sunburn.

 - Also important in those with photosensitivity.

     

    The effects of sun on the skin

     

    Short Term effects

    • Sunburn
    • Photosensitivity

     

     

    Long term effects

    • Skin cancer
    • Wrinkling
    • Solar Elastosis 
    • Solar keratoses / Actinic Keratosis
    • Seborrhoeic warts

     

    Skin Types (Fitzpatrick classification)

    This classification is important as it dictates the populations that may be more prone towards developing skin cancers. For example, individuals with Type 1 skin has the least protection from the sun's ultraviolet rays, and has the highest risk of developing skin cancer compared to other skin types. 

     

     

    skin_types

    Types, Causes and Distribution of skin cancers

     

    Types of skin cancer:

    • Melanoma skin cancer
    • Non-melanoma skin cancers - Basal cell carcinoma and squamous cell carcinoma.

     

    The main risk factor for most skin cancers is exposure to UV radiation in the absence of adequate melanin pigmentation. Other risk factors specific to each type of cancer will be covered later on. 

       

      Locations on body:

      Squamous cell carcinomas and actinic keratosis tend to occur at sites of high UVR exposure. Important areas include:

      • Dorsum of the hands.
      • Exposed scalps of bald-headed individuals.
      • Lower lip and ears.

       

      Basal cell carcinomas are most commonly found on the face.

      Melanomas are more commonly found on areas of intermittent sun exposure. This includes on the legs, back, under the nails and soles of feet.  However, pigmentation on nail beds may also obscure an underlying melanoma; a high-index of suspicion is needed when diagnosing and managing pigmented skin lesions.

       

        Pre-malignant skin conditions

        1) Actinic keratoses are small, red, scaly, areas on sun-exposed sites - they signify areas of dysplasia

        • Very common, often multiple lesions are found.
        • There is a low rate of progression to SCC.
        • Most lesions spontaneously involute.

         

        If an actinic keratosis rapidly increases in size, ulcerates, bleeds or becomes painful, suspect that the lesion may have transformed to an SCC.

        Management:

        • Liquid nitrogen - Very effective!
        • 5-fluorouracil - Useful for multiple lesions; however this treatment is cytotoxic.
        • Surgical curettage / excision if the lesions are not responsive to the above, or reconsider your diagnosis. 

         

        2) Bowen's Disease - slow-growing, reddish-brown, scaly lesions, often on the legs. These are areas of full-thickness dysplasia, which may lead to SCCs.  It is an important differential diagnosis of BCC.

         

        Management:

        Curettage - Remove and send for histological assessment

        Basal Cell Carcinoma (BCC)

        This is the most common human skin cancer. It is 5 times more prevalent compared to SCCs, and arises from the basal cells in the epidermis of the skin. 

        The history – usually “Nodular” (see image to right).

        • Often described as a "rodent ulcer".
        • It is a slow-growing, skin-coloured papule.
        • It contains a central ulcer – due to central necrosis.
        • The surface has edges that appear rolled, with a "pearly" surface and visible small vessels (telengactasia).
        • This may bleed spontaneously, but usually heals over.
        • BCCs are mainly benign. The most aggressive tumours may however, infiltrate perineural and perivascular structures. 

         

        Classic Nodular BCC

        Aetiology:

        • Genetic predisposition
        • UV radiation (therefore more common on the head and neck)
        • Immunosuppression
        • Arsenic poisoning / exposure. 

         

        Diagnosis - Mainly clinical, but if in doubt, histological examination of the biopsied lesion may confirm the diagnosis 

        BCCs may also be categorised as follows:

        1. Superficial

        • Superficial BCCs may be anywhere, and are found as multiple lesions rather than a singular lesion.
        • Appearance: Pink, irregular, scaly.
        • Slow-growing.

         

        2. Morphoeic  / Sclerosing

        • Appearance: Waxy; gray-coloured
        • Mostly found on the middle part of the face
        • May spread through infiltration of local nerves
        • May recur after treatment 

        3. Pigmented

        • May resemble a melanoma

         

        Management of BCCs:

        • Surgical removal - Important superficial structures at risk (depending on location) include the orbital nerves
        • Curettage and cautery
        • Radiotherapy
        • Photodynamic therapy

        The excised area is examined under the microscope to ensure that the entire lesion has been removed. If the tumour reaches the margin of the excised lesion, the dermatologist may opt to excise further, or observe the area closely.

        Cure rate  is >85%.

         

        Squamous Cell Carcinoma (SCC)

        Definition: This is a tumour of the squamous (keratin-producing)cells in the epidermis

         

        Features:

        • Locally invasive
        • Has the potential to metastatize
        • Is the second most common skin cancer

         

        Causes/Risk factors:

        • Chronic exposure to UV radiation
        • Fair-skin
        • Long term PUVA therapy (psoriasis treatment).
        • Radiation
        • Immunosuppression
        • Chronic wounds
        • Progression from Bowen’s disease or actinic keratosis

         

        SCC (Source: skin cancer awareness project

        Common sites (sun-exposed surfaces):

        • Face, lower lip, ears
        • Hands
        • Lower legs

         

        History:

        • Slow-growing nodule(s), which may be crusted and scaly; but may become warty and keratotic.
        • May present as an ulcer without keratinisation.
        • Starts with hyperkeratosis of the skin.
        • Tends to metastasise to local lymph nodes.

         

        Diagnosis - If an SCC is suspected, a biopsy is taken for histological confirmation. The histology report will include the degree of differentiation, the depth of the tumour and the margins of the excised specimen. 

         

        Prognosis depends on the site and the cause. There is a lower risk of metastatises if the cause is UV radiation, and it is not on the lip or ear. There is a higher risk of metastasis if the tumour occurs on a non sun-exposed area, and the risk is highest if it developed from Bowen's disease or a chronic ulcer.  

         

        Management:

        • Surgical excision and histological examination - If the tumour extends to the margins of the removed tissue, further excision is necessary.
        • A margin of >1mm is considered adequate.
        • Clinically enlarged local lymph nodes should be biopsied. Lymph nodes with positive findings are removed 
        • Curettage and cautery
        • Radiotherapy

        "In transit" metastases involves a locally spreading the tumour, which is discontinuous with the primary site.

         

        Melanoma

        Melanoma:

        Definition: Cancer of melanocytes, which are cells in the basal layer of the skin producing melanin. The number of melanocytes in both black and white people are similar, but the amount of pigment made varies.

         

        High mortality– 20%

         

        Epidemiology

        • Caucasian
        • Female
        • >35 years of age
        • Family history of melanoma
        • Number of moles
        • Previous naevus (40% melanomas develop from naevi)

         

         

        Melanoma - irregular border, >6mm, colour variation,  (Source: topnews.net.nz)

        Types:

        The following 3 types start with a horizontal growth phase occuring in the epidermis layer (This appears as an enlarging, pigmented macule/plaque that is considered "in situ"), before the vertical phase begins – at which point the cancer becomes invasive.

        1) Superficial spreading

        • The most common type; usually has an irregular margin and surface with variation in pigmentation across the lesion.

         

          2) Lentigo Maligna

          • Occurs on sun-damaged areas of the skin, particularly on the face, scalp, neck and hair follicles.

           

            3) Acral Lentiginous Melanoma:

              • Occurs on the peripheries and is not related to UV exposure
              • Surfaces affected include ears, palms, soles and the skin beneath nails.
              • It is associated with Hutchinson’s Sign (pigmentation of nail fold) - a sign that pigmentation of nail is due to melanoma.
              • Is more common in black and Japanese populations. 
              • Has a poorer prognosis.

               

              These 3 types tend to grow slowly until the vertical phase begins. At this point, they start to thicken and develop into a nodule. The timing at which this phase begins is unpredictable.

               

              The other types of melanomas have no horizontal phase – they develop as a pigmented nodule. The main type is thenodular melanoma:

              • It is more common in men, 50-60 years of age. 
              • There is a poor prognosis with early lymphatic spread.
              • It may occur on any part of the body.
              • It is sharply delineated from surrounding skin.
              • It can bleed / ulcerate.

               

              To describe or diagnose a suspected melanoma, the following acronym “ABCDE” may be applied:

              – Assymmetry

              B – Border irregularity

              – Colour variation

              D – Diameter >6mm

              – Evolving – enlarging or changing?

              Having more of these features strengthens the suspicion of the lesion being a melanoma

               

              Staging

              • Stage 1 - Localised lesion (70% 5-year mortality)
              • Stage 2 - Spread to regional lymph nodes
              • Stage 3 - Distant metastases (very high mortality)

               

                Prognosis

                Breslow's depth is used as a prognostic factor, and describes the depth of invasion of the tumour cells. The depth is calculated by evaluating the entire tumour obtained through excisional biopsy.

                 

                Management:

                Excision according to the Breslow Thickness Score is the gold standard. Breslow thickness is a reliable, widely-used measurement to guide the adequacy of the margins of the excised lesion. For example:

                • Melanomas < 1 mm in depth should have a 1 cm margin.
                • Melanomas > 1 mm in depth require a 2 cm margin.
                • Melanomas <2mm in depth require a 3cm margin 

                Clark’s levels is another measurement that can be used, which measures the layer of skin the melanoma has spread down to.

                Normally the excision is done in 2 stages. Firstly, to remove the lesion under local anaesthetic. This is sent for histology to confirm a melanoma and its thickness. Then the another excision is carried out to remove the margin.

                Following excision, regular checkups are required.

                 

                References

                 

                R J Motley et al. Multi-professional Guidelines for the Management of the Patient with Primary Cutaneous Squamous Cell Carcinoma. British Association of Dermatology.

                  

                NR Telfer et al. Guidelines for the management of Basal Cell Carcinomas.   BJD, Vol. 159, No. 1, July 2008 p35

                  

                J.R. Marsden et al. Revised U.K. guidelines for the management of cutaneous melanoma 2010. British Journal of Dermatology  pp238–25.

                  

                http://www.dermnet.com/ - Large database of images for skin cancers and other skin diseases.

                  

                Other references:

                Gawkrodger D. Dermatology: An Illustrated Colour Text. Churchill Livingstone; 4 edition. 

                Breslow A. Thickness, cross-sectional areas and depth of invasion in the prognosis of cutaneous melanoma. Ann Surg 1970; 172:902

                Clark, W.H., Jr.: A classifiation of malignant melanoma in man correlated with histogenesis and biologic behavior. In Montagna W, Hu F (eds): Advances in Biology and Skin, Vol 8, The Pigmentary System, Pergamon Press, New York, 1966: 612-647

                Fitzpatrick TB: Soleil et peau. J Med Esthet 1975;2:33034.

                 

                With thanks to disease-picture.com for allowing the use of their images in the production of this revision article. 

                Advertisement

                Fastbleep © 2019.